1. Field of the Invention
The present invention is directed to a polyamide graft copolymer which is composed of a polyamine moiety and grafted-on polyamide chains.
2. Discussion of Related Art
Graft copolymers based on polyamine and polyamide are known. They may be prepared, for example, by cationic polymerization of caprolactam in the presence of polyethyleneimine hydrochloride dendrimers as core molecule (J. M. Warakomski, Chem. Mater. 1992, 4, 1000-1004). Compared with linear nylon-6, nylon-6 dendrimers of this type a have markedly reduced melt viscosity and solution viscosity, but unchanged tensile strength, stiffness, melting points, enthalpies of fusion and barrier action with respect to oxygen.
Graft copolymers based on polyvinylamine and polyamide are known from U.S. Pat. No. 2,615,863. Further, U.S. Pat. No. 3,442,975 describes graft copolymers which are prepared by polymerizing lactams in the presence of high-molecular-weight polyethyleneimine.
DE-A 19 15 772 describes blends made from a polyiminepolyamide graft copolymer, and also from a polyolefin and/or polyester, which are processed to give fibers which are easy to color.
Finally, DE-A 196 54 179 describes H-shaped polyamides which are prepared from lactams or aminocarboxylic acids, from an at least trifunctional amine, from dibasic carboxylic acids and from monobasic carboxylic acid. There is a certain ratio here of the two last named compounds to one another and of these to the functional groups of the at least trifunctional amine. The products have improved melt stability.
Polyamide graft copolymers of this type are suitable, for example, as a blend component for providing a molding composition with better processing performance or better compatibility with other polymers. However, the compatibility of currently known graft copolymers, mainly containing nylon-6 graft chains, with respect to polyamides derived from a combination of diamine and dicarboxylic acid is not always ideal when these polyamides are used as a base for molding compositions.
There has to date been no disclosure of analogous polyamide graft copolymers which contain graft chains derived from a combination of diamine and dicarboxylic acid. A possible reason for this is that attempts to prepare them from diamine, dicarboxylic acid and a polyamine give a crosslinked product.
The object of the present invention, therefore, is to provide polyamide graft copolymers containing graft chains derived from a combination of diamine and dicarboxylic acid. This object has been achieved using a process as described below.
The present invention, therefore, provides a graft copolymer which contains the following monomer units:
a) from 0.5 to 25% by weight, preferably from 1 to 20% by weight and particularly preferably from 1.5 to 16% by weight based on the graft copolymer, of a polyamine having at least 11 nitrogen atoms and a number-average molecular weight (Mn) of at least 500 g/mol and preferably at least 800 g/mol;
b) a substantially equimolar combination of diamine and dicarboxylic acid as a polyamide-forming monomer; and
c) optionally, lactam and/or xcfx89-aminocarboxylic acid as a further polyamide-forming monomer, where these can provide not more than 95% by weight, preferably not more than 90% by weight, particularly preferably not more than 70% by weight and very particularly preferably not more than 50% by weight, of the polyamide graft chains.
The terms xe2x80x9csubstantiallyxe2x80x9d and xe2x80x9caboutxe2x80x9d in the present application are used to denote a value within 10% variation from the specified value.